The subject matter disclosed herein relates generally to gearboxes and more particularly to a method and system for estimating remaining life of a gearbox.
Gearboxes are used for power transmission in many systems such as, wind turbines, automobiles, and locomotives. A gearbox typically includes components such as a housing, shafts, bearings, and gears. Various gearbox designs are available to meet different speed transmission requirements. Two examples include a planetary gearbox and a helical gearbox.
Gears, bearings, and shafts in a gearbox may have defects, may fail over time, or may simply wear out. These damaged or worn components may be replaced after the damaged or worn condition is detected. However, taking a gearbox out of service for such replacement typically results in revenue loss. Instead, if the replacement is performed during a scheduled maintenance procedure, less loss occurs. Thus, knowledge of health of the key components of the gearbox can be used to enable effective maintenance. One of the parameters used in ascertaining the health of the gearbox is residual useful life (RUL), which is a function of the design of the gearbox, the components of the gearbox, and also the stress (number of cycles and number of peaks) the components experience during their operation. Any failure of individual components affects the RUL of the gearbox.
The design life of a gearbox typically is more than twenty years. However, several wind turbine gearboxes fail within four to five years. Conventional life calculation procedures are based on assumed operating profiles of the wind turbine. However in real operation, there could be significant variation in the operation profiles that could lead to gearbox life very different from that estimated during design. For example if there is unbalance in the rotor it creates an excess load on the bearing while in operation and that result into failure of bearing and hence the gearbox before its design life.